An OFDMA-based Hybrid MAC Protocol for IEEE 802.11ax

Two types of MAC mechanisms i.e., random access and reservation could be adopted for OFDMA-based wireless LANs. Reservation-based MAC is more appropriate than random access MAC for connection-oriented applications as connectionoriented applications provide strict requirements of traffic demands. On the other hand, random access mechanism is a preferred choice for bursty traffic i.e., data packets which have no fixed pattern and rate. As OFDMA-based wireless networks promise to support heterogeneous applications, researchers assume that applications with and without traffic specifications will coexist. Eventually, OFDMA-based wireless LAN will deploy hybrid MAC mechanisms inheriting traits from random access and reservation. In this article, we design a new MAC protocol which employs one kind of hybrid mechanism that will provide high throughput of data as well as maintains improved fair access policy to the medium among the terminals. The protocol works in two steps, where at step 1 sub-channels are approximately evenly distributed to the terminals and at step 2 terminals within in a subchannel will contend for medium randomly if the total number of terminals of the system is larger than the number of sub-channels. The details of the protocol is illustrated in the paper and we analyze the performance of our OFDMA-based multi-channel hybrid protocol using comprehensive computer simulations. Simulation results validate that our proposed protocol is more robust than the conventional CSMA/CA protocol in terms of throughput, collision reduction and fair access. In addition, the theoretical analysis of the saturation throughput of the protocol is also evaluated using an existing comprehensive model

Pattern of Childhood Malignant Tumour in the Paediatric Surgery Department of Bangabandhu Sheikh Mujib Medical University

Background: Childhood malignancy is fast becoming an important paediatric problem in Bangladesh. They differ markedly from adult malignancy in their nature and distribution. This is a 5 years retrospective study of childhood malignant tumour as seen at the paediatric surgery department of Bangabandhu Sheikh Mujib Medical University (BSMMU). Objectives: The objective of this study is to determine the types of malignant patients admitted in the paediatric surgery department of BSMMU and also to know their age and sex distribution. Methods: This is a 5 years retrospective study from January 2005 to December 2009 in the paediatric surgery department of BSMMU, Dhaka, Bangladesh. All admitted malignant patients, aged up to 15 years diagnosed by means of histological or cytological examination included in this study. Results: Seventy (70) malignant patients were admitted during the study period, 65.7% patients were male and 34.3% patients were female with a male female ratio of 1.9:1. Fifty two (74.3%) patients were below 5 years and eighteen (25.7%) patients were between 5 to 15 years. The Wilms’ tumour was the most common malignant tumour which accounted for 42.8%. Hepatoblastoma was the second most common (24.2%). The other malignant tumours were neuroblastoma (15.7%), Non-Hodgkins lymphoma (5.7%), Rhabdomyosarcoma (4.2%), malignant fibrous histocytoma (1.4%), Fibroscarcoma (1.4%), Osteosarcoma (1.4%), malignant sacrococcygeal teratoma (1.4%), carcinoma of the rectum (1.4%0. Conclusion: Based on the result of this study, Wilms’ tumour is the commonest paediatric solid malignancy in our country. Carcinoma of the rectum may rarely occur in paediatric age group. Key words: Frequency; malignant solid tumor; children. DOI: http://dx.doi.org/10.3329/bsmmuj.v4i2.8638 BSMMU J 2011; 4(2):99-10

Emotional Expression Detection in Spoken Language Employing Machine Learning Algorithms

There are a variety of features of the human voice that can be classified as pitch, timbre, loudness, and vocal tone. It is observed in numerous incidents that human expresses their feelings using different vocal qualities when they are speaking. The primary objective of this research is to recognize different emotions of human beings such as anger, sadness, fear, neutrality, disgust, pleasant surprise, and happiness by using several MATLAB functions namely, spectral descriptors, periodicity, and harmonicity. To accomplish the work, we analyze the CREMA-D (Crowd-sourced Emotional Multimodal Actors Data) & TESS (Toronto Emotional Speech Set) datasets of human speech. The audio file contains data that have various characteristics (e.g., noisy, speedy, slow) thereby the efficiency of the ML (Machine Learning) models increases significantly. The EMD (Empirical Mode Decomposition) is utilized for the process of signal decomposition. Then, the features are extracted through the use of several techniques such as the MFCC, GTCC, spectral centroid, roll-off point, entropy, spread, flux, harmonic ratio, energy, skewness, flatness, and audio delta. The data is trained using some renowned ML models namely, Support Vector Machine, Neural Network, Ensemble, and KNN. The algorithms show an accuracy of 67.7%, 63.3%, 61.6%, and 59.0% respectively for the test data and 77.7%, 76.1%, 99.1%, and 61.2% for the training data. We have conducted experiments using Matlab and the result shows that our model is very prominent and flexible than existing similar works.Comment: Journal Pre-print (15 Pages, 9 Figures, 3 Tables

An exploratory research on grammar checking of Bangla sentences using statistical language models

N-gram based language models are very popular and extensively used statistical methods for solving various natural language processing problems including grammar checking. Smoothing is one of the most effective techniques used in building a language model to deal with data sparsity problem. Kneser-Ney is one of the most prominently used and successful smoothing technique for language modelling. In our previous work, we presented a Witten-Bell smoothing based language modelling technique for checking grammatical correctness of Bangla sentences which showed promising results outperforming previous methods. In this work, we proposed an improved method using Kneser-Ney smoothing based n-gram language model for grammar checking and performed a comparative performance analysis between Kneser-Ney and Witten-Bell smoothing techniques for the same purpose. We also provided an improved technique for calculating the optimum threshold which further enhanced the the results. Our experimental results show that, Kneser-Ney outperforms Witten-Bell as a smoothing technique when used with n-gram LMs for checking grammatical correctness of Bangla sentences

IMPROVING THE PERFORMANCE OF OFDMA-BASED WI-FI NETWORK WITH HYBRID MEDIUM ACCESS CONTROL PROTOCOL DESIGN

Nowadays, the IEEE 802.11, i.e., Wi-Fi has emerged as a prevailing technology for broadband wireless networking. To meet the tremendous rise of demand for future generation wireless LANs, a robust and efficient MAC protocol is required for the Wi-Fi network. The acute rise of demand for high-speed wireless LANs has driven intensive research to improve the performance of MAC protocols leveraging a variety of MAC techniques. However, traditional MAC mechanisms are not suitable for next-generation communications due to some inherent constraints. In this regard, OFDMA technology could be adopted to design an efficient MAC protocol for the Wi-Fi network. The OFDMA technology supports multi-channel communications and hence ensures simultaneous communications between two or more users.The purpose of this research is to provide a high-speed network for Wi-Fi users. The thesis presents three MAC protocols, namely, HTFA (High Throughput and Fair Access), ERA (Efficient Resource Allocation), and PRS (Proportional Resource Scheduling), by employing the OFDMA technology. The novel protocols improve Wi-Fi communication using the latest IEEE 802.11ax standard, i.e., Wi-Fi 6. In particular, the protocols improve several performance parameters of the MAC protocol, such as increasing the throughput, goodput, fairness index, and reducing the packet retransmissions, collisions, etc. The researcher designs the models and illustrates the working principles for the intended Wi-Fi protocols. The performance of the protocols is evaluated through comprehensive computer simulations using a powerful network simulator, i.e., NS-3. The saturation throughput is also measured effectively by constructing the analytical models. Simulation results validate that the new protocols are far better than the existing protocols.The protocols designed in this thesis are compliant with the latest IEEE 802.11ax standard that promises to enhance the throughput (simply data rate) at least four times per user and support ten times users. Thus, the new protocols can ensure uninterrupted and smooth communication in highly dense environments (e.g., stations, airports, markets) where a large number of Wi-Fi users may need to send a massive volume of data concurrently. The thesis contains a lot of resources such as the state of the art of MAC protocols, analysis of contemporary protocols and their performance matrix; architecture of Wi-Fi system, OFDMA constraints and regulations; framework of protocols; relevant data, theory, and methods; analytical models; experimental results and analyses; etc. that would be the valuable resources to the future researchers for the research on the Wi-Fi network.Nowadays, the IEEE 802.11, i.e., Wi-Fi has emerged as a prevailing technology for broadband wireless networking. To meet the tremendous rise of demand for future generation wireless LANs, a robust and efficient MAC protocol is required for the Wi-Fi network. The acute rise of demand for high-speed wireless LANs has driven intensive research to improve the performance of MAC protocols leveraging a variety of MAC techniques. However, traditional MAC mechanisms are not suitable for next-generation communications due to some inherent constraints. In this regard, OFDMA technology could be adopted to design an efficient MAC protocol for the Wi-Fi network. The OFDMA technology supports multi-channel communications and hence ensures simultaneous communications between two or more users.The purpose of this research is to provide a high-speed network for Wi-Fi users. The thesis presents three MAC protocols, namely, HTFA (High Throughput and Fair Access), ERA (Efficient Resource Allocation), and PRS (Proportional Resource Scheduling), by employing the OFDMA technology. The novel protocols improve Wi-Fi communication using the latest IEEE 802.11ax standard, i.e., Wi-Fi 6. In particular, the protocols improve several performance parameters of the MAC protocol, such as increasing the throughput, goodput, fairness index, and reducing the packet retransmissions, collisions, etc. The researcher designs the models and illustrates the working principles for the intended Wi-Fi protocols. The performance of the protocols is evaluated through comprehensive computer simulations using a powerful network simulator, i.e., NS-3. The saturation throughput is also measured effectively by constructing the analytical models. Simulation results validate that the new protocols are far better than the existing protocols.The protocols designed in this thesis are compliant with the latest IEEE 802.11ax standard that promises to enhance the throughput (simply data rate) at least four times per user and support ten times users. Thus, the new protocols can ensure uninterrupted and smooth communication in highly dense environments (e.g., stations, airports, markets) where a large number of Wi-Fi users may need to send a massive volume of data concurrently. The thesis contains a lot of resources such as the state of the art of MAC protocols, analysis of contemporary protocols and their performance matrix; architecture of Wi-Fi system, OFDMA constraints and regulations; framework of protocols; relevant data, theory, and methods; analytical models; experimental results and analyses; etc. that would be the valuable resources to the future researchers for the research on the Wi-Fi network

MATLAB-based vibration signal processing for fault diagnosis

Traditionally, vibration signal processing has been performed using analog and digital signal analyzers or writing code in intermediate and high-level computer languages. However, the advent of higher-level interpretive-based signal processing software products such as MATLAB has added a new dimension to vibration signal processing. This paper presents a method for analyzing motor vibration data using MATLAB. The method first pre-processes the vibration data to remove noise and baseline wander. Then, the frequency spectrum of the vibration signal is calculated using the Fourier transform. The frequency spectrum is then used to identify the dominant frequencies in the vibration signal. These dominant frequencies can be used to identify potential problems with the motor, such as bearing defects or misalignment. The method was studied on a set of vibration data collected from open source online data of a real motor. The results showed that the method was able to identify the dominant frequencies in the vibration signal accurately. The method was also able to identify the potential problems with the motor. This paper demonstrates the effectiveness of using MATLAB for analyzing motor vibration data. The method presented in this paper can be used to improve the reliability and efficiency of motor maintenance

IoT-Based Intelligent Gas Leakage Detection and Fire Protection System

Gas Leakage and its fatal effects are a great concern throughout the world, especially in developing countries like Bangladesh. Every year lots of people died and countless damages to assets occur due to the fire caused by the gas leakage. Not only that but gas leakage and explosion are also very harmful to the climate. Thus, a system to detect gas leakage and preventive measures is of utmost importance. In this project, we design and implement an intelligent IoT prototype to detect gas leakage, and the fire caught by gas leakage. Our goal is to minimize the effect of gas leakage by taking some protective measures. When the gas sensor, detects the gas leakage, the solenoid valve shuts off the gas line, and the exhaust fan starts to run. Again, when the flame sensor detects a fire, the sucker throws the fire extinguisher balls to the fire. The GSM SIM module notifies the user by sending a message to his smartphone. The buzzer sounds when a mishap occurs and the LCD monitor always shows the status of the system. In this way, we have efficiently designed and implemented a low-cost and intelligent gas leak detection and fire suppression system

Community People Preparedness and Response on Prevention and Control of COVID-19 Best Practice in Bangladesh

Purpose: The major objectives of the study were to assess the knowledge, attitude & practice (KAP) towards community preparedness and response on prevention of COVID-19 among the community people. Method: A sample survey was conducted to collect data from people admitted to a district-level tertiary hospital for the treatment of various health complications during the COVID-19 pandemic. A total of 300 randomly selected patients and their attendants were interviewed in the hospital setting. Results: The mean knowledge score was 18.73 out of 24 and the main sources of information were TV (86.5%), radio (13%), newspaper (13%), social media (13.5%), friends/relatives (14%), formal healthcare providers (6%) and religious leaders (3%). Knowledge was significantly poor among aged people, women, less educated, and less earning. The majority of the participants (79%) suggested wearing facemasks as effective tools to prevent COVID-19 from spreading, whereas 56% mentioned maintaining physical or social distance as crucial to prevent the infection. We found strong relationship between monthly total family expenses and wearing of facemasks by gender to prevent the COVID-19 (x2= 18.405; Cramer’s V= .17, df = 8; sig; P= < .018). Similarly maintaining physical/social distance to prevent COVID-19 is also related to respondents’ economic strata (x2= 43.741; Cramer’s V= .14, df = 20; Sig; P= < .002). Conclusions: Awareness program on COVID-19 is very important to prevent the spread of the deadly virus.  Effective communication intervention with increasing treatment facilities is essential for the prevention and control of COVID-19. Government and development agencies should prioritize the COVID-19 response program with regular health care services.